The invention relates to machines for making brochures and like accumulations of folded sheets. Machines to which the present invention pertains include those known as gather-stitchers wherein one or more staples are used to connect the backs of accumulated folded sheets to each other.
Presently known gather-stitchers operate with drum-shaped singularizing devices which remove successive sheets from a stack by grasping the folded backs of individual sheets. The backs of the withdrawn sheets are caused to strike an abutment, and the thus oriented sheets are opened up by pairs of drums which engage the front edges of the sheets and accelerate the opened sheets on their way toward a saddle-like chain conveyor or a saddle-like rail whereon the opened sheets are transported past one or more additional sheet-admitting stations and on to a stapling station. The accumulations of stapled-together sheets are ejected from the machine by moving them transversely of the direction of travel along the conveyor or along the rail and by depositing them on one or more belt conveyors.
A drawback of conventional gather-stichers and similar machines is that their output is limited because each and every sheet must be individually transported through the machine so that a higher output can be achieved only by increasing the speed of individual sheets. Moreover, only a fraction of a machine cycle is available for the treatment of sheets, such as opening, stapling and ejecting. The speed of individual sheets cannot be increased at will, especially since each sheet is caused to abruptly change the direction of its movement as soon as it reaches the conveyor or the rail as well as immediately upon completion of the stapling operation. Even the most recent types of presently known gather-stitchers cannot turn out in excess of five brochures or the like per second.
Attempts to increase the output of conventional gather-stitchers and analogous machines include reducing the number of changes in the direction of movement of individual sheets. Reference may be had to German Offenlegungsschrift No. 26 31 058. However, the machine of this German printed publication still exhibits a number of drawbacks, such as the need to completely singularize each and every stack of folded sheets (so that a high output can be achieved only by increasing the speed of advancement of sheets from the feeding stations to the stapling station) as well as the fact that only a small fraction of the machine cycle is available for the application of one or more staples to an accumulation of sheets. Still further, the machine which is disclosed in the German printed publication relies on opening of folded sheets exclusively under the action of gravity and centrifugal force. Such mode of opening is not sifficiently reliable because electrostatically charged sheets or sheets whose folded-over panels adhere to each other under the action of freshly applied printing ink are not likely to be opened up with a required degree of predictability. Therefore, the output of such machines is still below that which is desirable in a modern paper processing plant.
Published European patent application No. 95 603 discloses a machine which is similar to that of the aforediscussed German printed publication except that the saddles resemble the rungs of ladders and are closely adjacent to each other. Even though the panels of opened sheets extend downwardly beyond the saddles, the European application does not disclose any means for stabilizing the downwardly extending panels at elevated speeds of the sheets and/or the manner of stapling the accumulated sheets to each other. As a rule, a reliable stapling operation necessitates the utilization of clinching devices which must be guided with a high degree of accuracy in order to cooperate with the staple applying devices so as to predictably deform the legs of staples upon penetration of the legs through the accumulations of sheets at the stapling station. The downwardly extending panels are likely to flutter while the sheets advance at an elevated speed so that they do not permit for predictable introduction of clinching devices. The provision of clinching devices directly on the saddles would contribute to the initial and maintenance cost of the machine, and the clinching devices would have to be guided with a high degree of precision in order to properly register with the mobile staple applicators at the stapling station.
Swiss Pat. No. 584,153 discloses means for stuffing one or more inner sections into the jackets of newspapers or the like. The jackets are introduced into the pockets of a rotating wheel with their folded backs leading, and the jackets are thereupon moved in the axial direction of the wheel and are opened up to provide room for one or more inserts. Each jacket completes one revolution about the axis of the wheel and is opened up as well as shifted axially during such revolution. The patented machine has sheet opening means only between the jacket feeding and the insert admitting stations. The opening means of the patented machine are not suited for predictable opening of sheets, especially if each sheet is a composite sheet having first and second groups of panels joined to each other along the back of the composite sheet. Still further, the backs of folded sheets in the bottom portions of pockets in the rotating wheel are not accessible to stapling or other sheet connecting devices.
Additional sheet gathering machines are disclosed in commonly owned U.S. Pat. Nos. 4,080,678 and 4,511,132.